Horizontal turning lathe, as a high-speed, high-efficiency, and cost-effective production material, is easy to operate, simple in process, and greatly reduces labor waste. However, sometimes internal or external failures such as unstable machining accuracy may occur, which increases the difficulty of troubleshooting. The manufacturers of CNC lathes summarized nine reasons for the unstable machining accuracy of CNC lathes to help you deal with them.
1. The size of the workpiece is accurate, and the surface finish is poor
The cause of the failure: the tool tip is damaged and not sharp; the machine tool resonates and the placement is not stable; the machine tool has crawling phenomenon; the processing technology is not good.
Solution: After the tool is worn or damaged, it is not sharp, then re-sharpening or selecting a better tool to re-calibrate the tool; the machine has resonance or is not stable, adjust the level, lay the foundation, and fix it smoothly; the cause of mechanical crawling is drag The plate guide rail is severely worn, the ball screw is worn or loose, the machine tool should be maintained, and the iron wire should be cleaned after work, and lubricated in time to reduce friction; choose a coolant suitable for workpiece processing, if it can meet the processing requirements of other processes In this case, try to choose a higher spindle speed.
2. The phenomenon of taper and small head on the workpiece
The cause of the failure: the level of the machine is not adjusted properly, one high and one low, resulting in uneven placement; when turning the long axis, the contribution material is harder, and the tool eats deeper, causing the tool to give way; the tailstock thimble is not concentric with the spindle.
Solution: Use a level to adjust the level of the machine tool, lay a solid foundation, and fix the machine tool to improve its toughness; choose a reasonable process and appropriate cutting feed to avoid the tool being forced to give it to the knife; adjust the tailstock.
3. The phase light of the driver is normal, but the size of the processed workpiece is sometimes large and sometimes small
The cause of the failure: long-term high-speed operation of the machine tool carriage causes the screw and bearing to wear; the repeated positioning accuracy of the tool post produces deviations during long-term use; the carriage can accurately return to the starting point of processing every time, but the size of the workpiece is still changing. This phenomenon is generally caused by the main shaft. The high-speed rotation of the main shaft causes serious wear of the bearing, leading to changes in machining dimensions. Metal processing WeChat, the content is good and worthy of attention.
Solution: Use a dial indicator to lean on the bottom of the tool post, and edit a fixed cycle program through the system to check the repeat positioning accuracy of the carriage, adjust the screw gap, and replace the bearing; use the dial indicator to check the repeat positioning accuracy of the tool post, Adjust the machine or replace the tool post; use the dial indicator to check whether the workpiece is accurately returned to the starting point of the program, if possible, repair the spindle and replace the bearing.
4. The size of the workpiece is different from the actual size by a few millimeters, or there is a big change in a certain axis
The cause of the failure: the rapid positioning speed is too fast, the drive and the motor can't react; the mechanical carriage screw and the bearing are too tight after long-term friction loss; the tool post is too loose after tool change, and the lock is not tight; the edited program Error, the head and tail do not respond or the tool compensation is ended; the electronic gear ratio or step angle of the system is set incorrectly. High-speed precision turning and milling machine tool
Solution: If the rapid positioning speed is too fast, adjust the GO speed appropriately, and the cutting acceleration and deceleration and time will make the drive and motor work normally at the rated operating frequency; after the machine tool wears out, the carriage, the screw rod and the bearing are too tight If it is stuck, it must be re-adjusted and repaired; if the tool post is too loose after tool change, check whether the reversal time of the tool post is satisfied, check whether the worm gear inside the tool post is worn, whether the gap is too large, whether the installation is too loose, etc.; if it is a program If the cause is caused, the program must be modified, improved in accordance with the requirements of the workpiece drawing, a reasonable processing technology is selected, and the correct program is written in accordance with the instructions of the manual; if the size deviation is found to be too large, check whether the system parameters are set properly, especially the electronic gear and Whether the step angle and other parameters are damaged, this phenomenon can be measured by using a dial indicator.
5. The effect of machining arc is not ideal, and the size is not in place. Small and medium-sized CNC lathe
The cause of the failure: the overlap of the vibration frequency causes resonance; the processing technology; the parameter setting is unreasonable, the feed speed is too large, and the arc processing is out of step; the looseness caused by the large screw gap or the out of step caused by the screw is too tight; the timing belt Wear.
Solution: Find out the resonant parts, change their frequency to avoid resonance; consider the processing technology of the workpiece material, and make a reasonable program; for the stepper motor, the processing rate F cannot be set too large; whether the machine is installed firmly, placed smoothly, and dragged Whether the plate is too tight after being worn, the gap is increased or the tool holder is loose, etc.; replace the timing belt. Metal processing WeChat, the content is good and worthy of attention.
6. In mass production, occasionally the workpiece is out of tolerance
Cause of failure: The tooling and fixture must be carefully checked, and the operator's operation method and the reliability of the clamping must be taken into account. Due to the size change caused by the clamping, the tooling must be improved so that the worker may try to avoid misjudgment by human negligence; the CNC system may When the external power supply fluctuates or is interfered, it will automatically generate interference pulses, which will be transmitted to the drive and cause the drive to receive excess pulses to drive the motor to take away or to run less.
Solution: Understand the law, try to use some anti-interference measures, such as: isolation of strong electric cables with strong electric field interference from signal lines of weak electric signals, adding anti-interference absorption capacitance and shielding wire isolation, in addition, check the ground wire Whether the connection is firm and the grounding contact is nearest, take all anti-interference measures to avoid interference to the system.
7. There is a change in the processing of a certain process of the workpiece, and the size of the other processes is accurate
Cause of failure: Whether the parameters of the block program are reasonable, whether they are in the predetermined trajectory, whether the programming format meets the requirements of the manual
Solution: If there are random teeth in the thread program segment, and the pitch is wrong, it immediately associates with the peripheral configuration (encoder) of the thread processing and the objective factors of the function.
8. Each process of the workpiece has an increase or decrease phenomenon
Reasons for failure: programming errors; unreasonable system parameter settings; improper configuration settings; mechanical transmission components change regularly and periodically.
Solution: Check whether the instructions used by the program are executed in accordance with the required track specified in the manual. You can judge by hitting the dial indicator. Position the dial indicator at the beginning of the program and whether the carriage returns to the starting position after the end of the program, and then repeat the execution Even if you observe the results and master the rules; check whether the system parameters are set reasonably or considered to be changed; whether the relevant machine tool configuration meets the requirements in the connection calculation coupling parameters and whether the pulse equivalent is accurate; check whether the transmission part of the machine tool is damaged, gears Whether the coupling is uniform, check whether there are periodic and regular failure phenomena, and if so, check the key parts and eliminate them.
9. Unstable dimensional changes caused by the system
Causes of failure: unreasonable system parameter settings; unstable operating voltage; system is affected by external interference, causing the system to lose synchronization; capacitors have been added, but the impedance between the system and the driver does not match, resulting in the loss of useful signals; signals between the system and the driver Abnormal transmission; system damage or internal failure.
Solution: Whether the speed, acceleration time is too large, whether the spindle speed, cutting speed are reasonable, whether the parameter modification of the operator causes the system performance to change; install a voltage stabilizing device; make sure that the ground wire is reliably connected, and the pulse output contact of the driver Add anti-interference absorption capacitors; select the appropriate capacitor model; check whether the signal connection line between the system and the driver is shielded and whether the connection is reliable; check whether the system pulse signal is lost or increased; send it to the factory for repair or replacement of the motherboard.
